Control device



Nov. 5, 1957 R. A. ALCOTT 2,812,404

CONTROL DEVICE Filed D60. 8, 1955 INVEN TOR. ROLLINA. ALCOTT UnitedStates Patent Ofiice 2,812,404 Patented Nov. 5, 1957 CONTROL DEVICERollin A. Alcott, St. Louis Park, Minn., assiguor toMinueapolis-Houeywell Regulator Company, Minneapoiis, Minm, acorporation of Delaware Application December 8, 1955, Serial No. 551,94612 Claims. (Cl. 200-140) This invention relates to a control device andmore particularly to a room thermostat. My invention concerns a novelmeans for control point adjustment and calibration. In responsivedevices there are often problems of the switch contacts welding due toarcing at near make or break. My invention also concerns a novel meansof forcing the contacts apart in case of a weld between the contacts.

An embodiment of my invention that accomplishes this desirable resultconsists of a switch arm pivoted relative to a base or frame withcooperating contacts being carried by the switch arm and base. The pivotpin or member determining the pivotal axis of the switch arm is guidedin a cam means attached to the base and is spring biased into journaledslots in the cam means. A spring means biases the switch arm to a normalposition with the contacts closed. The switch actuator applies a forceto the switch arm opposing the spring bias and when the force is greatenough to overcome the spring bias it will separate the contacts. If thecontacts become welded to prevent their separating the actuator willthen move the switch arm such that the pivot pin moves in the journaledslots in the cam means forcing movement of the contacts relative to eachother and therefore cause the contacts to separate.

Therefore an object of my invention is to provide an electric switch ofthe slow make and break variety.

Another object of my invent-ion is to provide a means for separatingwelded contacts in slow make and break electric switches.

Yet another object of my invention is to provide a novel means forcontrol point adjustment and actuation of a control device including anelectrical switch.

Further objects of my invention will become evident upon inspection ofthe following drawings, specification and claims.

Figure 1 is an elevation of an embodiment of my invention.

Figure 2 is a partial plan view of the embodiment of Figure 1 of myinvention.

Figure 3 is a plan view of a portion of the embodiment of Figure 1 of myinvention.

Figure 4 is a perspective view of the portion of the embodiment ofFigure 1 shown in Figure 3.

Figure 5 is a fragmentary view showing the switch arm and pivot of theembodiment of Figure 1.

Figure 6 is a fragmentary view showing the cooperating contacts as seenfrom the right in Figure 1.

In the drawings a base 10 has a recessed portion or chamber 11 coveredby a plate 12 fitted in the base 10. A switch 13 within the chamber 11is constructed as follows. A switch arm 15 positioned in the chamber 11has journaled slots 16 as best seen in Figure 5, which cooperate with apivot pin 18. The pivot pin 18 has spring extensions 19 and 20 extendingat right angles to the pivot pin 18 that cooperate with the base 10 asbest seen in Figure 1. A cam is attached to the base 10 in 2 the chamber11 and has journaled slots 26 therein that cooperate with the pivot pin18. The spring extensions 19 and 20 bias the pivot pin naled slots 26 inthe cam 25.

the base 10 carries a stationary contact 30 positioned for cooperationwith a contact 31 carried by the switch arm 15. A compression spring 32engages the switch arm 15 and base 10 biasing the switch arm 15 to aposition with the contacts 30 and 31 engaged. The switch arm 15 carriesa bearing plate 34 positioned for cooperation wtih an actuating rod 35journaled in the plate 12.

The switch 13 functions as follows. position as shown in Figure 1, thespring and 20 of the pivot pin 18 bias the pivot pin 18 to the top ofthe journaled slots 26 and bias the switch arm 15 about the pivot pin 18counterclockwise engaging the contacts 30 and 31. Upon a displacement ofthe actuating rod 35 downward the switch arm 15 will rotate clockwiseabout the pivot pin 18 against the bias of the spring 32 and disengagethe contacts 30 and 31. However, if the contacts 30 and 31 weld togetherand resist disengagement, then displacement of the actuating rod 35downward will cause the switch arm 15 to rotate counterclockwise aboutthe contacts 30 and 31 with the pivot pin 18 moving downward in thejournaled slots 26. Movement downward of the pivot pin 18 in the slots26 will cam the switch arm 15 to the right due to the angle of the slots26. This will create a shearing action between the contacts 30 and 31which together with the pivotal action between the contacts 30 and 31will break the contact weld and separate the contacts 30 and 31. Uponseparation of the contacts 30 and 31 the spring extensions 19 and 20will bias the pivot pin 18 back into position at the top of thejournaled slots 26. Upon a condition change with the actuating rod 35retracted in the plate 12 the spring 32 will rotate the switch arm 15counterclockwise about the pivot pin 18 and the contacts 3%) and 31 willagain be engaged.

The condition sensing means 38 as shown in Figure 1 is supported on thebase 10 by a plurality of brackets 48, an integral part of the circularplate 42. The plate 42 has a circular opening centrally located coveredby a flexible diaphragm 44 which together with a dished coverplate 46form a chamber 48 containing a temperature responsive liquid. A stud 50attached at its head to the diaphragm 44 and positioned thereby is inscrew threaded engagement with a nut 53. The nut 53 has a cylindricalportion 54 which cooperates with a bearing member 56. The bearing member56 is attached in fixed relation to the plate 12 and base 10 by acircular member 58 attached to the base 10. The periphery of thecircular member 58 is formed to provide a decorative wall plate. Thebearing member 56 guides the nut 53 allowing axial movement of the nut53. The bottom of the nut 53 cooperates with the actuating rod 35 totransmit any temperature change to the switch mechanism 13 as a changein position of the actuating rod 35.

The nut 53 has a conical surface 60 which is engaged by a spring spidermember 62 as shown best in Figures 3 and 4. Extensions 63 on the spidermember 62 are attached to a rotatable member 65 and positioned thereby.The spring spider member 62 exerts a force upward on the nut 53 at theconical surface 60 sufiicient that friction between the spider member 62and the nut 53 will cause the nut 53 to be positioned angularly by thespider member 62. The relative axial position of the nut 53 on the stud50 will determine the temperature at which the condition sensing means38 will cause a 18 to the top of the jour- A bracket 29 attached to In anormal extensions 19 change in position of the actuating rod 35 andoperation of the switch 13.

A manual adjusting member 68 is attached to the rotatable member 65 andcarries an index 69 that cooperates with indicia of temperature 71 onthe cover plate 4 6 for controlpoint setting.

Calibration of the control point setting of the device is obtained byholding the nut 53 from rotation and rotating the manual adjustingmember 68 with the spider member slipping on the nut 53 to obtain theproper relation between indicated temperature and switch position. Anelectrical connector 72 connects the switch arm to-a terminal 73, andthe bracket'29 is provided with a terminal 75. v

'Iihe embodiment described has particular utility as a slow actionswitch and thermostatic device though I do not intend to limit myinvention to the embodiment shown nor to the use in thermostatic devicesbut to limit my invention only as defined in the appended claims.

I claim as my 'invention;

1. In a device of the type described, a base member, a switch arm, apivot pin for said switch arm, a normally stationary contact, a contactcarried by said switch arm for cooperation with said stationary contact,a first spring means biasing said switch arm to a normal position withsaid contacts in cooperation, a condition sensing means applying a forceto said lever arm in opposition to said first spring means, a conditionchange pivoting said switch arm about said pivot pin, a cam attached tosaid base cooperating with said pivot pin, and a second spring meansbiasing said pivot pin to a normal position rela tive to said cam, saidpivot pin movable along said cam upon said contacts failing to separate,movement of said pivot pin along said cam causing said switch arm tomove said contact relative to said stationary contact.

2. In a device of the type described, a base member, a switch arm, apivot pin forming a pivotal axis for said switch arm, cooperatingcontacts carried by said switch arm' and said base, spring means biasingsaid switch arm to a normal position with said contacts in engagement, acondition sensing means applying a force to said lever arm in oppositionto said spring means, a cam attached to said base, and journaledportions in said cam means forreceiving said pivot pin, said springmeans biasing said pivot pin into said journaled portions of said cam,said pivot pin movable along said cam in said journaled portionsuponsaid contacts failing to separate, movement of said pivot pin alongsaid cam moving said switch armand said contacts relative to each other.

3. In a device of the type described, a base member, a switch arm,cooperating contacts carried by said switch arm and said base, a pivotpin forming a pivotal axis for saidswitch arm, a cam attached to saidbase cooperating with said pivot pin, journaled portions in said cam,spring means biasing said switch arm to a normal position and said pivotpin to engagement of said cam in said journaled portions of said cam,and a condition sensing means applying a force to said switch arm opposing said spring means, movement of said pivot pin along said cam surfacecausing movement of said switch arm and movement of said contactsrelative to each other.

4. In a device of the type described, a base member, a switch arm, apivot pin forming a pivotal axis for said switch arm, cooperatingcontacts carried by said switch arm and said base, spring means biasingsaid switch arm to a normal position, a condition sensing means applyinga force to said switch arm opposing said spring means, and a camattached to said base cooperating with said pivot pin, movement of saidpivot pin along said cam surface causing movement of said switch arm andmove ment of said contacts relative to each other.

5. In a device of the type described, a frame, a switch arm, a pivotingmeans providing a pivotal axis for said switch arm in said frame,cooperating contacts carried by said switch arm and said base, springmeans biasing said switch arm to a normal position, actuatin meansapplying a force to said switch arm opposing said springmeans, and a camsurface integral to said frame, jour..v

naled portions in said cam surface cooperating with said pivoting means,movement of said pivoting means along said cam surface causing movementof said switch arm and movement of said contacts relative to each other.

6. In a device of the type described, a frame, a switch arm, a pivotingmeans providing a'pivotal axis for said switch arm in said frame,cooperating contacts. carried by.

a switch arm, a stationary contact carried by said base;-

a contact carried by said switch arm for cooperation with saidstationary contact, a cam means attached to said base, journaled slotsin said cam means for receiving said pivot pin, a spring means biasingsaid switch arm to a normal position with said pivot pin in saidjournaled slots, a condition sensing means applying a force to saidswitch arm opposing said spring means, movement of said pivot pin insaid iournaled slots along said cam surface causing movement of saidswitch arm and movement of said contacts relative to each other. 7

8. 'In a device of the type described, a base member, a switch arm, apivot pin forming a pivotal axis for said switch arm, a first contactcarried by said base, a second contact carried by said switch arm forcooperation with said first contact, a first spring means biasing saidswitchj arrn such that said contacts are in engagement, a conditionsensing means applyinga force to said switch arm opposing said firstspring means, a condition increase pivoting said switch arm about saidpivot pin separating said contacts, a cam attached to said basecooperating with said pivot pin, journaled portions, apart of said cam,a second spring means biasing said pivot pin into engagement with saidjournaled portions of said cam, movement of said pivot pin along saidcam means when said contacts fail to separate upon a condition increase,said movement of said pivot pin along said cam means causing movement ofsaid switch arm and said second contact relative to said first contactand hence separation of said contacts, said second spring meansreturning said pivot pin to engagement with said journaled portions ofsaid cam upon separation of said contacts.

9. A condition responsive device comprising a frame, a conditionresponsive element, a rod axially positionable by said element inaccordance with condition value, a nut cooperating with threads on saidrod and having cylindrical and conical outer surfaces, a manual memberpivoted in said frame about an axis concentric with said nut, a spidermember carried by said manual member frictionally engaging the conicalsurface of said nut, the angle of said conical surface of said nut suchthat normally there is sufiicient friction between said nut and saidspider member that said nut will rotate upon rotation of said spidermember, cooperating indicia on said frame and said manual memberexhibiting'condition value in accor .ance with the angularly adjustedposition of said nut, and a switch means actuated by the axial positionof said' nut.

10. A condition responsive device comprising a frame, a conditionresponsive element, a rod axially positionable by said element inaccordance with condition value, a nut cooperating with threads on saidrod and having cylindrical and conical outer surfaces, a manual memberpivoted in said frame about an axis concentric with said nut, aspider'member carried by said manual member frictionally engaging theconical surface of said nut, cooperating indicia on said frame and saidmanual memher exhibiting condition value in accordance with theangularly adjusted position of said nut, and a switch means actuated bythe axial position of said nut.

11. A condition responsive device comprising a frame, a conditionresponsive element, a rod axially positionable by said element inaccordance with condition value, a nut cooperating with threads on saidrod, a manual member pivoted in said frame about an axis concentric withthe threads on said nut, an engaging means carried by said manual membercooperating with said nut, cooperating indicia on said manual member andsaid frame exhibiting condition value in accordance with the axialposition of said nut, and a switch means actuated by said nut.

12. A condition responsive device comprising a base, a conditionresponsive element, a plurality of brackets supporting said conditionresponsive element extended forward from said base, a stud axiallypositionable by said element in accordance with condition value, a nutcooperating with threads on said stud and having cylindrical and conicalouter surfaces, a manual member pivoted in said frame about an axisconcentric with the threads on said nut, a spring spider member carriedby said manual member frictionally engaging the conical surface of saidnut, the angle of said conical surface of said nut being of a value thatnormally the spring bias of said spider member creates suflicientfriction between said nut and said spider member that said nut willrotate upon rotation of said spider member, portions of said manualmember extending radially beyond said brackets but allowing rotation ofsaid manual member between said brackets, an adjusting member carried bysaid portions of said manual member, cooperating indicia on saidadjusting member and the outer surface of said condition sensing elementexhibiting condition value in accordance with the angularly adjustedposition of said nut, and a switch means actuated by the axial positionof said nut.

References Cited in the file of this patent UNITED STATES PATENTSDillman et al. Apr. 30, 1940 Weber et al. Nov. 15, 1949 Fuchs Jan. 3,1950

